This invention relates, in particular, to a fuel metering and injection system for mixture compressing, externally ignited internal combustion engines. The system includes a fuel line and a metering valve in the fuel line, the valve having a movable valve member which, especially when the movable valve member is embodied as a slide valve piston, meters out to the air quantity streaming through a suction tube a quantity of fuel in a desired proportion. The movable valve member (slide valve piston) can be actuated by a fluid of changeable pressure to influence the metering process. It is the purpose of such fuel metering and injection systems to create automatically a favorable fuel-air mixture for an internal combustion engine, in order to burn the fuel as completely as possible and, therefore, to avoid or to reduce greatly the formation of toxic exhaust gases, while maintaining the highest possible performance or the lowest possible fuel consumption of the internal combustion engine. For this purpose, the desired ratio between air quantity and fuel quantity must be changeable in dependence on engine parameters, such as rpm, load, temperature and exhaust gas composition. Such an adjustment should be possible by the simplest means, i.e., by a simple intercession in the control loop mechanism of the fuel injection system.
In a known fuel injection system of the abovedescribed kind, the slide valve piston is actuated by a mechanical air measuring element via a lever against a nominally constant return force (pressure fluid).
While this known prior art installation has the advantage that, by the use of a liquid pressure medium, it is relatively simple to produce a constant return force, which is easily changeable, there results the disadvantage of a mechanical transmission of the measured air value to the slide valve piston. Because of this fact, supplementary limits are placed on the regulation with respect to intercession in the control loop of the system.